(i) Technical Field
The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device.
(ii) Related Art
Recently, a CSP (Chip Size Package) is being used in order to downsize a semiconductor device. The CSP is flip-chip mounted on a printed circuit or the like with use of a solder ball. When a current is applied to the semiconductor device via the solder ball, the solder may diffuse into a foundation layer acting as an interconnection line. In this case, an electrical open or an electrical short may occur, and the semiconductor device may be broken. In order to restrain the diffusion of the solder, an anti-diffusion layer may be used. Japanese Patent Application Publication No. 2000-353763 discloses a method in which a layer having a thickness of approximately 70 μm and formed with a copper is formed on a resin, and a solder ball is formed on the Cu layer. The Cu layer acts as the anti-diffusion layer.